Catalytic conversion of hydrocarbon oils



0mm Ohm om@ Omo OQO OMG ONO O m OOO Omw O00 0h Gww on@ O3 OME ONQ O m 00m00- 3 Shets-Sheet -24 l VE`NT0RS f" ATTORNEY DuBois EASTMAN CHARLES Run-MER DU Bols EA`s'rMAN r-:TAL

CATALY'IIIC CONVERSION OF HYDROCARBON OILS Filed March 18, 1941 C) 80 O O G D h Bevo NI'DS aad'sa-laanssaad \l A oom Oow June 12, 1945.

Oom

THEIR y June 12, l945l Du Bols EAST-MAN ET AL CATLYTIC CONVERSION OF HYDROCARBON OILS s sheets-sheets Filed March 18, 1941 um .0E

ooou+ CHARLES RICHKER DUBOIS EAST-MAN INVENTORS THEIR ATTORNEY enema June iz, 194s UNITED STATE s PATENT oFF-ICE CATALYTIC CONVERSION F HYDROCARBON OILS au Bois Eastman and charles nichker, Port Arthur. Tex., assignors, by mesne assignments,

to The Texas Company, New York, N.

poration of Delaware Application March 18, 1941, Serial No. 383,900

Claims. (Cl. 196-52) ,ily converted to carbon or coke upon contact with the catalyst. The so' heated oil is then passed to a catalytic reaction 'zone advantageously without delay during which undesired non-catalytic reactions might occur.

It has been proposed in the prior art relating to cracking of oil to heat the oil rapidly to a cracking temperature without substantial cracking occurring and thereafter passing the heated oil to a reaction zone wherein the reaction is effected without the additionof further heat. The object heretofore was to avoid the deposition of carbon in the heating coil which deposition caused localized overheating of the coil resulting in splitting the heating coilupon continued exposure to heating.

We have found, however, that even though the oil feed to a catalytic cracking reaction is heated under conditions such that no carbon formation occurs in the heating coil or heating zone nevertheless the conditions-of heating may still be so severe that hydrocarbon products are formed which are highly susceptible to 'carbon formation upon contact with a solid pulverulent porous adsorptive type of conversion catalyst. The carbon -forming bodies so formed appear to lbe readily a preheated stream of the oil in substantially vanorized form through a catalyst bed maintained at an elevated temperature for a comparatively Y., a corline hydrocarbons with concomitant vbreakdown of a portion of the feed to gas. and resultant deposition of coke or carbon'on the catalyst. The activity of the catalyst, as measured by the percentage conversion to gasoline and gas, drops oil? exceedingly rapidly and at the same time the carlbon deposit builds up on the catalyst. In order to maintain a. desirably high conversion it has been customary to run with an exceedingly short conversion period or onstream time, then terminate the flow of the hydrocarbon charge through the catalyst bed and reactivate that bed by passing therethrough a highly heated gas containing air or oxygen to burn off the carbon deposits and bring the catalyst back to a high activity. In such operations it has been customary to employ an operating procedure such that the lthat when excessive quantities of carbon were deposited on the catalyst bed the reactivation could only be accomplished with exceedingly great difficulty and often without a return Vof the catalyst to adesired high activity. For these reasons resort had been made to short onstream periods.

However, as disclosed in our co-pending application, Serial No. 313,654, led January 13, 1940.

.now U. S. 2,319,590, it has lbeen found that contrary to the previous knowledge, greatly improved results are secured under proper and controlled operating conditions by employing 'a conversion period or onstream time which ls increased many times over previous practice. Further the proper reactivation of the catalyst is effected with a reactivation period which is not greater than and is usually less than the conversion period.y Greatly increasedl throughput and higher eiiiciency of operation of the plant are thereby secured.

As disclosed in our aforementioned pending application these improved results are accomplished by: (l) selecting a charging stock, preferably relatively free from unsaturated constituents, which is relatively clean and of good color, namely, havshort conversion time to convert the oil to gasolng a carbon residue of less than 0.2%and a color of less than 200 as measured on the Lvibond scale using a 1/2 inch cell; (2) employing a cracking catalyst of high and sustained activity;

and (3) correlating the operating conditions of temperature, pressure and space velocity with other factors to' allow prolonging the conversion time to a period not less than one hour and preferably of the order of 8 to 20 hours or more.

It was found that under these conditions the catalyst with deposited carbon or coke at the termination of the onstream time can be reactivated without difficulty with a reactivation period not greater than 4 hours and generally of the order of 2 to 3 hours. It was also found that under these conditions the conversion rate drops of! only a comparatively small amount as the conlversion period is prolonged to within the range set forth above, while the rate of carbon deposition on the catalyst falls E a comparatively large amount. Conversion yields in excess of 50 pounds and generally of the order of 80 pounds or more of gasoline plus gas per pound of carbon deposited on the catalyst are obtained. lAt the same time the ratio of v.gasoline to gasproduced is maintained at a desirably high figure and the quality of the gasoline is at least as good as that produced with the short conversion period.

In accordance with the present invention we have found that while selection of the feedstock is important, nevertheless the character of the heated stock just`prior to initial contact with the catalyst is also important. seemingly, the heated stock should be substantially free from certain highly unstable bodies having pronounced Y coke forming tendencies and which are formed where the voil has been subjected to severe conditions of heating. We have found that the tendency of a given stock to decompose into carbon on'contact with the .catalyst may be largely inhibited provided suitably controlled conditions prevail in the heating zone.

Desirable conditions ofheating exist when the oil undergoes no change in composition as indicated, for example, by the absence of any reduction in its fiash'poi'nt as the result of the heating in the heating zone.

The severity of thermal conditions prevailing lwithin a given heating coil can be indicated by -determining the soaking volume factor of the dicate that when the soaking volume factor has a value of about 1.0 the carbonaceous deposit on the catalyst is about 1 to 2% by weight of the feed oil passed to the catalytic reaction zonea On theother hand, when the soaking volume fac-V tor isabout 0.05 the carbonaceous deposit is reduced. to about 0.3 to 0.5% by weight of the charge The equation for the soaking volume fa tor is Where F=soaking volume factor of that portion of the heating coil wherein the oil is at a temperature of 800 F. and aboye;

L=barrels` per day of liquid oil through the coil measured at 60 F.;

t=the temperature of the oil F. alongthe coil between the point where the oil is at a temperature of 800 F. and the point at which the oil is'v dischargedthis outlet temperature, as indicated in Figure 1, may be as. high as l150 F.;

V=the internal volume in cubic feet of the coil between the points where t equals 800 F. and t equals the discharge outlet temperature;

Y (for pressures below pounds per square inch gauge)=antilogm(.8929 logmP-L7858);

Y (for pressures above 100 pounds per square inch gauge)=antilogm(l.709 log 10P-3.418); and

P=pressure in pounds per square inch gauge along the coil between the points where t equals 800 F. and t equals oil outlet temperature.

. Hereinafter the portion of the heating coil between the point where the oil temperature t equals 800 F. and the point where if; equals outlet temperature will be referred to as the V portion of the coil for convenience.

In an actual heating coil the temperature progressively increases while 'the pressure progressively decreases toward the outlet. Therefore, the reaction constant K must vary with the tempera-r R=antuog (16emeture throughout the coil so that the effective value of soaking volume factor" F is an integratlon of the values of thesoaklng volume factor for sinali sections of the heater.

Also thevapor being heated in the V portion of the coilis in that portion of the coil a long or short time depending onwhether the pressure is high or low. Accordingly a given temperature range with a given feed rate produces greater cracking 1n the heating coil at high pressure than at low pressure. Therefore it is necessary to ernploy a pressure correction factor Y.

It is generally accepted in the art that the relationship between the reaction velocity constant and temperature may be expressed by the Arrhenius equation which is:

E is the energy of activation in B. t. u. per l :pound mol;

p is the gas law'constant, namely, 1.9864 B. t. u.v

The constant a in the equation varies for dierent stocks, While E, the energy of activation, is essentially the same for all stocks as explained in the article by Geniesse and Reuter entitled Reaction-velocity constants of oil cracking, Industrial Engineering Chemistry, vol. 24, No. 2, Pages 219-222, 1932. Since this is the case the ratio of the reaction velocity constant at any given temperature to that at any other temperature is approximately the same -for all cracking stocks. These authors determined E as having a value of 53,400 gram calories per gram mol (equivalent to 96,120 B. t. u. per pound mol), but calculations based on more recent data indicate avalue of 94,000 B. t. u. per pound mol.

. For practical purposes a base temperature of laavaaea 800 F. isconveniently chosen as a base temperature in the ordinary coil heater wherein the oil is exposed to elevated temperatures momen- (e) (8004-1160) which upon simplification becomes (--E' -E R=e (SOOHBO) pci-460) and which may be written as The curve in Figure '1 of the drawings shows the relationship between R and temperature over a wide range of temperature, namely, about 800 to 1150 F., and within which range R may have al value ranging from 1 to about 3800 as'indicated on the drawings.

In determining the pressure correction factor Y it is first necessary to establish the relationship between the soaking volume factor F and the tper cent conversion to .gasoline at various pressure' levels in a heating coil in which there is no'substantial pressure gradient. Taking the relationship for the- 100 pounds per square inch gauge pressure level as a, basic or reference pressure level the pressure correction factor is the f ratio of the soaking volume factor at the reference pressure level to the soaking volume factor at any other desired level to give the same per cent conversion to gasoline. The reference pressure level is conveniently chosen as one within or in close proximity to the average pressure prevailing in the V portion of the heating coil.

Gasoline is considered as a product having a increments in the coil. beginning with the point at which the hydrocarbon is at the chosen base temperature, for example, 800 F., against the corresponding volume of the coil between the point corresponding to the chosen base temperature and each successive temperature point. Curve A in Figure 3A is a typical example.

From Figure I1 the value of R can be determined lfor each corresponding temperature point on curve A and the values for R can then be plotted as ordinates against the corresponding partial coil volumes as abscissae thereby forming the curve B of Figure 3B. By partial coil volume is meant the volume of the coil between the point corresponding to the 'base temperature and each successive temperature point. The quotient of the area under the curve of Figure 3B divided by V represents the integrated average of R.

The pressure gradient curve for the V portion of the coil is plotted as curve C of Figure 3C by plotting actual coil pressures at successive points. beginning with that corresponding to the chosen base temperature used in plotting curve A, against the corresponding volume of the coil between the chosen base point and each .successive pressure point. From' Figure 2 the value of the pressure correction factor Y Acan be determined for each pressure point on curve C and the values of Y can be plotted as ordinates against the corresponding partlal coil volumes as abscissae thereby forming the curve D ofFigure 3D. The quotient of the area under the curve of Figure 3D divided by V represents the integrated average of Y.

The R and Y curves are combined to form a consolidated (RY) curve. This is done by selecting a partial coil volume and reading the cor.

responding values of R and Y. The products ofthe values of R and Y are plotted against the corresponding partial coil volume points giving the consolidatedcurve E of Figure 3E.

400 F. end point and a Reid vapor pressure value of 9.5 pounds. The curve in Figurezof the drawings represents graphically the relationship between :pressure /and pressure correction factor Y. The equation of the curve of Figure 2 for pressures above 100 pounds per square inch gauge' may be written as:

As previously mentioned the temperature progressively increases through the V portion of the heating coil and therefore it is necessaryto determine the temperaturegradient in this portion of the coll. This is arrived at by plotting each actual temperature at successive points or area- V where t=800 F.

so that V wheret outlet temperature 1v1-:.11: R Y 1V V where t=='800 Ff In cases where the transfer lines are large and where there is appreciable free space between the heating coil outlet and the catalyst itself.A

these volumes should be included as a part of the V portion of the coil and 'the calculation made as described above.

In the foregoing manner the soaking volume factor for any given coil heater installation can be determined readily. The preferred heating conditions contemplatedl by our invention are realized when the soaking volume factor does not exceed about 1.0 and is preferably in the range 0.05 and below as previously mentioned.

Oil may be heated under conditions such that there is no substantial cracking as measuredl by prior art standards. Yet if the heating is under such conditions that the soaking volume factor" exceeds 1.0 the carbon deposition upon subsequent contact with the cracking catalyst will still be excessive. examples.

This is borne out by thefollowing f action temperature. y passed from the heating oil through a catalytic In these examples the feedoil was a virgin gas oil having an A. P. I. gravity of 37; a 50% boiling point of about 528 F.; a Conradson carbon content of 0.01%; and derived from Oklahoma crude. i

'I'he oil was passed in a continuous stream through a coil heater under a pressure of 50 pounds gauge wherein it was heated to the re- The heated oil vapors were reactor packed with a catalyst comprising a synthetic silica-alumina-zirconia material.

The onstream period for each' reactor extended for a period of 4 hours following which the catalyst was reactivated in the usual manner and again placed onstream. the operation being repeated for 6 cyclesat each set of temperature conditions. y

During each regenerating period therate of flow of the oxygen containing regenerating gases fed to the reactor undergoing regeneration was held at a constant measured rate andthe composition of the gases entering and leaving the reactor determined at frequent intervals. lThe quantity of carbonaceous material removed from the catalyst during regeneration was then determined by integrating the increase in carbon monoxideand carbon dioxide content oflthe gases over the regenerating period and multiplying -by the quantity of regenerating gas used. These figures were verified .by calculating the carbon deposition from the consumption of oxygen during the regenerating period.

The "soaking volume factor of the heating coil was varied primarily by increasing the length of thev portion of the coli in lwhich the oil was at a temperature above 800 F., thereby increasing the lengthof time of exposure of the oil tohigh temperatures. i

The following tabulated data provide a comparison of the carbon deposition on the catalyst with diierent heating conditions prevailing in the heating coil: f

tor which is substantially below 1 and in the range .05 and below. i

Factors which may be used to control the soaking volume factor in a given operation include:

(1) Injektion of steam or otherinert ciment such as canbon dioxide in the .feed to the heating coil;

y(2) Employment of a large ratio of heating surface to volume of heating coil and/or employ ment of a high rate of heat transfer;

(3) Avoidance of excessive pressure drop through the heating coil; and

(4) Avoidance of localized overheating of the coil.

In the foregoing experiments a synthetic silica-alumina-zirconia type catalyst was used. However, it is contemplated that other catalysts may be employed. Various acid-treated and metal-substituted clays, such as the Super-Filtrols, are satisfactory. Likewise, the acid-treated and metal-substituted natural or artificial zeolites, such as the artificial zeolite kown as Doucil, can be used. Various metals can be substituted in the clays or zeolites, such as uranium, molybdenum, manganese, lead, zinc, zirconium, nickel and the like. Likewise, the combination of certain acid-treated active clays of the characte of Filtrol, together with added proportions of alumina or silica or both can be employed. Alumina alone may be used under certain conditions. The synthetic silica-allumina catalysts can be improved by the addition of other constituents. such as zirconium oxide or molybdenum oxide. Other catalysts which are not silica-alumina, catalysts, either synthetic or prepared from natural minerals, have been 'found which satisfy the characteristics of the catalyst of the present invention. Examples ,of other suitable catalysts comprise metallic halide compounds such as the halides of aluminum and chromium, etc. In gens eral, a catalyst is em'ployed which is stable at high temperatures of the` order of 1400 to` 1600 .45- F., as determined rby calcining in a muilie furnace at that temperature, and which is a measure or indication of theA ability of the catalyst to maintain its activity under the customary temperatures of reactivation of the order of 1100 to 1400 F., as measured by thermocouples within the catalyst bed during the reactivation cycle. It is preferred to employ a catalyst which is substantially free from alkali. and alkaline earth A v B C D E Average reactor temperature., 908 9L? 945 951 955 Soaking volume factor- 0. 024 0. 051 0. 071 0. 216 1. 30 Carbon deposited on eatal st, percent by weig tofieed oil 0. 30 0. 32 0. 88 l. 07 1. 52 Gasoline l yield, percent byvol.cffeed 20.8 24.8 28.1 23.0 427.0 Gas yield, percent by weight 10. 8B 1l. 31 12.44 l2. 1l 16. 13

1400. end point gasoline having a Reid vapor pressure oi 0.5 pounds.

As the foregoing data indicate the carbon deposition becomes quite substantial where the heating coil is operated with a soaking volume' factor in' excess of about 1. Even in run E v where carbon deposition on the catalyst was excessive no carbon deposition in the heating coil could be detected. y From the standpoint of economic operation of acatalytic process with long onstream periods, it

lis desirable that the carbon deposition does not exceed about 1.0% by weight of the feed.

For example, with an operation giving a 20% V.conversion to gasoline during an 8 hour onstream period it is desirable that the carbon deposition should not exceed about 0.2%. With a 30% `conversion it is desirable that the carbon deposition should not exceed 0.3%. Therefore, in order to realize these conditions it is essential to employ a soaking volume iacmetals.

While a stationary catalyst bed has been referred to it is also contemplated that the invention is applicable to other types of catalytic reaction systems including the so-called fluid catalyst system wherein a finely powdered catalyst is suspendedwithin the reaction zone in the presence of the hydrocanbons undergoing treatment.

Also if desired the conversionv reaction may be carried out in the presence of light gases including hydrogen which may be recirculated through -the4heating and conversion zones or through the conversion zone only.

Although the invention has particular applicationv in the conversion of gas oil and other high boiling hydrocarbons, it may =be employed in effecting catalytic conversion of various types of .hydrocarbons at elevated temperatures.

Obviously many modifications and variations c of the invention,l as hereinbefore set forth, may

'be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the ap'- uously through a stationary mass of the active pended claims. cracking catalyst for at least about 4 hours with- We claim: out interruption for reactivation of the catalyst.

1. In a continuous process for the manufacture of high antiknock gasoline by catalytic conversion of a feed oil at cracking temperatures, the steps which comprise passing a stream of gas oil having a carbon residue less than 0.2% and a color less than 200 on the Lovibond 1/2 inch cell through a tubular heater, heating the stream therein to a temperature in the range 800 to 1150 1i'. under conditions auch that the soaking volume factor" (referred to a coil having a pressure characteristic of 100 pounds per square inch gauge) does not exceed 0.05 as determined by the equation:

V when t outlet temperature RxYX-dv V when 1-800 F.

1 Filz where F=soaking volume factor of -that portion of the heating coil wherein the oil is at a temperature of 800 F. and above;

L=barrels per day of liquid oil through the coil measured at 60 F.:

ft=tne temperature or the on in F. along the Y. (for .pressures above 100 poundsl=antii0gxn (1.709 logro P3.418); Y (for pressures `below 100 pounds) =antilogro (.8929 logro P-1.7858) 4. In a continuous process for the manufacture of high anti-knock gasoline by catalytic conversion of a feed oil at cracking temperatures, the steps which comprise passing a stream of gas oil having a carbon residue less than 0.2% and a color less than 200 on the Lovibond 1/2-inch cell through a tubular heater, heating the stream therein to atemperature in the range 800 to 1150 F. under conditions such that the soaking volume factor (referred to a coil having a pressure characteristic of 100 pounds per square inch gauge) does not exceed 0.05 as determined by the equation:

V where t-outlet temperature 1i'}J f RxYxdv where F=soaking volume factor of that portion of the heating coil wherein the oil is at a temperature of 800 F. and above;

Le-barrels per day of liquid oil through the coil measured at 60 F.;

At=tne temperature of the ou incr'. along the Y (for pressures above 100 pounds) =antilos1o (1.709 logro P-3.418)I A Yv (for pressures below 100 pounds) =antlloglo P=pressure in pounds along the coil between the points where t equals 800' F. and tequals th outlet temperature of the oil; A l

and thereafter subjecting the thus heated oil in vapor form to the action of an active synthetic silica-alumina-zirconia cracking catalyst maintained at a temperature in the range 800 F.

P=pressure in pounds'i along the coil between the points where t'equals 800 F. and t equals the outlet temperature of the oil;

and thereafter subjecting the thus heated oil in vapor form to the action of a solid active cracking f lcatalyst stable at 1400 to 1600 F. and at a temv perature in the range 800 F. and above, thereby and above, thereby eifecting substantial conversion of feedoil into gasoline hydrocarbons.

2. The method according to claim 1 in which 4the "soaking volume factor is in the range about vthostrearnofheatedoilvapor-iapassedelmtin-oy effecting substantial conversion of feed oil into gasoline hydrocarbons.

nu Bols EASTMAN. cnsnms aroma. 

